Moisture separation from granular materials



y 1951 F. J. FONTEIN I 2,982,411

MOISTURE SEPARATION FROM GRANULAR MATERIALS Filea July 23, 1956 3Sheets-Sheet 1 May 2, 1961 F. J. FONTEIN MOISTURE SEPARATION FROMGRANULAR MATERIALS 3 Sheets-Sheet 2 Filed July 23, 1956 FIG. 4

May 2, 1961 F. J. FONTEIN MOISTURE SEPARATION FROM GRANULAR MATERIALS 3Sheets-Sheet 3 Filed July 23, 1956 INVENTOR Faisal J. Fomsm ATTORNEYSUnited States Patent MOISTURE SEPARATION FROM GRANULAR MATERIALS FreerkJ. Fontein, 'Heerlen, Netherlands, assiguor to Stamicarbon N .V.,Heerlen, Netherlands The present invention relates to moistureseparation from granular materials and more particularly to a processand apparatus for eifecting the complete or partial removal of moisturefrom fine-grained material of substantially uniform compositioncontaining an amount of free moisture such that the pores between thegrains of material are partially filled with liquid.

. The invention is especially applicable to the treatment of material ofsuch small particle size that due to the capillary rise, the liquid inthe fine pores between the particles is only expelled from the materialif a given force is exerted thereon, as, for example, in completely orpartially removing moisture from fine coal, crushed ore and otherfine-grained materials.

A well-known practice for effecting the removal of liquid from suchmaterial embodies the use of centrifuges having a perforated wall inwhich the liquid is driven towards the wall of the basket under theinfluence of centrifugal force and forced out through the perforations.However, centrifuges of this type are subject to severe wear with theresult that their maintenance is costly.

It has also been suggested to effect the dewatering of granular materialby means of conical centrifuges having imperforate walls. With this typeof centrifuge the material to be treated is supplied through the centerof the centrifuge so as to form a moving layer therein. At or near theedge of the imperforate wall a slot is formed through which the liquiddriven towards it by the centrifugal force can issue. However, this slotserves only as an outlet for the water. Should fine-grained material,such as filter slurry or the like, be treated in a centrifuge of thistype either the slot' would have to be made so narrow as to becomeobstructed by the slurry or the slurry would,

together with the liquid, be forced out through the slot so that theapparatus would no longer accomplish its purpose.

It has further been suggested to store the fine-grained moist material,such as fine coal or the like, in bunkers where the liquid'is allowed tosettle into the lower part. After the material has remained in thebunkers for a given length of time, during which period a separation hastaken place into an upper layer of low liquid content and a lower layerof high liquid content, the lower layers are extracted from a fewbunkers and deposited in a storage bunker where the liquid is againallowed to settle or is removedfrom the material in some other way.Next, the drier part is discharged separately from each bunker. Thisconstruction has the distinct disadvantage of requiring a large bunkerspace.

Accordingly, it is an object of the present invention to provide animproved apparatus and method for effecting the complete or partialremoval of moisture from finegrained material of substantially uniformcomposition containing free moisture which substantially overcomes thedisadvantages outlined above.

Another object of the present invention is the provision of an apparatusof the type described which is' continuare provided for recycling themoisture-rich ice A further object of the present invention is theprovision of an apparatus of the type described having im-v proved meansfor forming and supporting a continuously moving layer of moisture ladenfine-grained material so that the moisture therein will becomeconcentrated in a fractional layer thereof during its movement.

A still further object of the present invention is the provision of anapparatus of the type described having improved means for separating themoisture concentrated fractional layer from a moving layer of moistureladen fine-grained material.

Still another object of the present invention is the provision of anapparatus of the type described which is simple in construction, easy tooperate and economical to operate and maintain.

A still further object of the present invention is the provision of animproved process for effecting the removal of liquid from fine-grainedmaterial of substantially uniform composition containing free moisturewhich includes forming a continuously moving layer of such material,supporting the moving layer so that the moisture therein will becomeconcentrated during its movement in a fractional layer thereof andseparating the moisture concentrated fractional layer from the movinglayer.

These and other objects of the present invention will become moreapparent during the course of the following detailed description andappended claims.

The invention may best be understood with reference to the accompanyingdrawings wherein an illustrative embodiment is shown.

In the drawings:

Figure 1 is a vertical sectional view of an apparatus embodying theprinciples of'the present invention;

Figure 2 is a top view of the apparatus shown in Figure 1;

Figure 3 is a somewhat schematic side elevational view of another formof apparatus embodying the principles of the present invention;

Figure 4 is a view similar toFigure 3 showing another form ofapparatus;'

Figure 5 is a diagrammatic longitudinal sectional view of a stillfurther form of apparatus;

Figure 6 is a fragmentary view showing a modification of the separatingmeans of the apparatus of Figure 5; I

stationary flat table 1, over which a number of blades or scrapers 2,2', of which only a few are shown, are moved in the direction indicatedby the arrow. To this end, the blades 2, 2' are fastened to endlesschains 3, 3', trained about a pair of spaced gear wheels 4. The gearwheels may be driven by any suitable driving mechanism (not shown).

The table 1 may have any suitable length and the material to be treated,e.g. filter slurry, is supplied to one end thereof from a funnel 5. Nearthe other end of the table, a slot-like opening 6 is provided, whichextends perpendicular to the longitudinal axis of the table. A slide 7includes a projecting lip 9 which, at a distance from the underside ofthe table, can shut off the entire slot-like opening 6 over a certainlength. Beneath the lip 9 a funnel 10 is disposed in which themoisture-rich product is collected. Conduits 11 and 12 and a pump 13product collected in the funnel 10.

The operation of the apparatus is as follows: From the funnel 5, whichis fed in a manner not illustrated in the drawing, a layer of suitablewidth of the material to be treated fiows continuously onto the table,where it is taken along by the blades or scrapers 2, 2, and Where alayer A of a certain thickness is formed.

At the start, the layer A has a uniform moisture content, but as thelayer is transported the liquid sinks and in the bottom part of layer A,a layer B of higher moisture content is formed, which layer graduallybecomes thicker, topped by a layer C having a moisture content whichgradually becomes smaller than the original content. At the slot-likeopening 6, the whole layer B or part of it may be discharged. Thisdischarge can be controlled by means of the lip-shaped projection 9, ashere a sloping face 14 is formed, the angle of which depends on themoisture content of the material. However, when a certain moisturecontent is exceeded, the material will start to flow across the edge ofthe lip. By changing the position of the slide 7 a greater or smalleramount of wet material may be discharged. The drier portion C of thelayer is discharged at 15, and the moisture-rich material is returned toa suitable place in the feed of funnel through conduits 11 and 12, bymeans of pump 13.

If very wet material is being treated, the table 1 may be wholly orpartly perforated, if desired, in order that excess amounts of liquidwhich may have sunk into layer B, may be removed therethrough. It isevident that other devices for moving the layer may also be used withoutdeparting from the invention eg a scraper chain, or the like.

In Figure 3, where corresponding parts have been denoted with the samereference figures as in Figures 1 and 2, the table 1 is formed by anendless belt 17, which moves on rollers 18 in the direction indicated bythe arrows. The material to be treated is supplied through funnel Satthe one end as before. At the other end there is provided a horizontallydisposed plate 19, which is preferably adjustable in the verticaldirection. The layers B and C are separated, by means of the plate 19,after which layer B flows into the funnel and is recycled, whereas layerC is discharged at 15.

The apparatus illustrated in Figure 4 comprises a flat table 21, which,as shown, has the construction of a screen mounted at an angle to thehorizontal plane greater than the angle of repose of the natural slopeof the wholly or partially moisturefreed product to be discharged. Theupper end of the table or screen 21 connects to the delivery end of asieve bend 22 (see my copending application Serial No. 475,251, filedDecember 14, 1954, now Patent No. 2,916,142), onto which the material tobe treated, e.g. water and fine coal, is tangentially fed, as from 23.The larger part of the water plus part of the fine product are collectedin the collecting tank 24 of the sieve bend and discharged at 25. At theend of the table 21 there is provided a pair of blades 27a and 27bconstituting a controlling element which can pivot around a horizontalshaft 26 and parallel to the underside of the table 21. The controllingelement blade 27a at the screen side of the table 21 projects beyond thescreening deck, and the blade 27b projects at the other side of thescreening deck.

A slot 28 is defined between the controlling element blades 27a and27band the lower end of table 21. Under the table 21 a collecting tank 29,which ends in a funnel 30, is provided. The discharge 31 of this funnel,into which also the overflow of the blade 27b opens, leads to a pump 32,the delivery pipe of which is connected to a conduit 33 leading to thefeed side'of sieve bend 22.

It will be understood that the underside of the collect ing tank 29 maybe closed by a wall, which is indicated at 34 by a dotted line, and thewater admitted through the screen is discharged as at 35, if desired.-According to the invention, the blades 27a and 27b of the controllingelement may be positioned at an angle to each other, which angle isadjustable.

Any suitable means may be provided for effecting this adjustment, oneexample of such a means being shown in Figure 7. As shown in Figure 7,the blades 27a and 27b are flat plates connected at one end to thehorizontal shaft 26 by means of hinges 51 and 52. The shaft 26 issupported by a frame, generally indicated at 50. Adjusting means in theform of turnbuckles 53 are hingedly connected at their ends at 54 and 55between the plates 27a, 27b respectively and the frame 50 and serve toadjust the position of the plates 27a and 27b relative to each other.Each turnbuckle 53 comprises a spindle 56 pro vided with left and righthand threads and housings 57 and 58 with corresponding inner threads,hingedly connected to the frame 50 and one of the plates 27a, 27b. Asshown in the drawing, shaft 26 is parallel to the lower edge of thescreen 21 and is positioned substantially in the elongation of thescreen 21. The latter is supported by angleirons mounted on the frame(not shown). The dryer material is collected in tank 60.

The overflow from sieve bend 22 falls onto the sloping table 21 andslides downwards until it is checked by the blade 27a. The watercontained in the coal sinks to the bottom layer and part of it dripsthrough the screen 21 into the collecting tank 29, resulting in theupper layer of bed A becoming drier. The controlling element 27a and 27bis now so adjusted that the blade 27a takes up a position at which theupper surface 36 of the bed C is so inclined that the drier coal slidesacross the edge of the blade 27a. The wet coal, which is contained inthe bottom part B of layer A can be discharged into funnel 30 throughslot 28 and across blade 27b, which has been given the most suitableposition to this end, after which this coal can be returned to the startof the process by means of pump 32 and through conduit 33, Wet fine coalis delivered only if it has a moisture content of, e.g. 40%.Measurements indicate that the decrease in moisture content of the dryfine coal effected in this way can be about 5%.

In Figure 5 there is shown a centrifuge 42, in which the moving layer isformed on a smooth imperforate wall 41 by centrally feeding the materialto be treated into the centrifuge from a funnel 43. Separated from thecentrifuge wall 41 by an annular slot 44, a conical or cylindrical body45 is provided over the upper edge of the centrifuge, which body ispositioned at an angle to the wall 41. A conical or cylindrical wall 46is connected to the lower edge of the body 45 so that material forcedout through the slot 44 is checked by the wall 46. Under the slot 44there is a collecting tank 47 for the moisture-rich material, which maybe recycled by means of devices of the nature previously indicated, butnot shown in the drawing. At the upper edge of the body 45 there isprovided a discharge device for thematerial that is completely orpartially freed of liquid, which device is not shown in the drawing. Thecentrifuge 42 is made to rotate by means of a motor 48.

The moving layer is here formed on the bottom of the centrifuge andmoves upwards along the conical wall 41, the liquid contained in thematerial being forced towards the wall by the centrifugal force, so thata moisturerich layer and a drier layer are formed on the wall and closerto the axis of the centrifuge, respectively. The moisture-rich layer canescape through the slot 44 and is checked by the Wall 46, so that thedischarge of too great an amount of material at that place is prevented.The amount discharged may be controlled by vertical shifting of the body45, 46.

Figure 6 shows a modification of the separating means of Figure 5. Theannular slot 44 is formed by a conical or cylindrical wall 45', thelower end of which is on the inside of the wall 41. The layer which hasbeen separated off is checked by a horizontal wall 49 and a .material tobe. treated to form the layer.

vertical wall 46'. The width of the slot canbe controlled by verticalshifting of the body 45, 49.

thematerial or in some'other part correspondingtherewith and thenseparating the lower part from the overlying part.

Naturally, whena fine-grained material containing an amount of freeliquid such that the pores between the grainsrof material are partiallyfilled with liquid is spread outin layer formation, the liquid containedtherein will settle into the lower part of" the layer where it will beretained either wholly or partially due to capillary action and it isthis latter part that. is separated by the process of the presentinvention. It is well known that fine.- grained material may, atdifferent moisture contents, form slopes of different gradients, butalso that such slopes cease to exist when the moisture content exceeds agiven maximum value in which case the material starts flowing togetherwith the liquid, which characteristic is utilized in the presentinvention to eifect separation.

For this reason the separation and removal of the parts with the higherand lower moisture contents according to the invention is preferablyeffected by the adjustment ofthe means of separation disposed at or nearthe end of the layer, which causes the material, at predeterminedmoisture contents, to form a slope with a gradient corresponding withthepredetermined contents, so that the material having a moisture contentlower than that to which the slope has been adjusted, or equal to orhigher than that at which the material starts flowing together with themoisture, is automatically carried oif along the means of separation.

The moving layer formed may extend horizontally or pass along the wallof a centrifuge in a direction away from the axis of. rotation and at anoblique angle to it.

Experiments made by the applicant on the removal of moisture from filterslurry in a centrifuge with a perforate wall and in a centrifuge with asmooth wall, in which the lowermost moisture-rich layer was removed andrecycled, have shown that the moisture content of the remaining layerwas about equal in both cases, so that it is recommendable to replacethe centrifuge wall which issubject to severe wear by a smoothwall andto cut otf the lowermost layer. According to the invention, however, thelayer may also travel downwards along an inclineunder the influence ofits own weight.

The invention also contemplates the provision of various apparatus whichserve to perform the above process and comprise means defining a surfacefor supporting a moving layer andmeans for continuously supplying theMoreover, means of separation is provided at or near the end of thesupporting surface for the purpose of separating the layer high inmoisture content and the layer low in moisture content from one another,in addition to which, means are provided for carrying oif the separatedfractions.

, Preferably, the means for separating the layer into a fraction high inmoisture content and a fraction low in moisture content can be disposedrelative to the supporting plane so that at least part of the materialconstituting the layer is enabled by the means to form a slope, thegradient of which depends on a predetermined moisture content ofthematerial, permitting the material having a moisture. content lower thanthat to which the slope has been adjusted or equal to. or higher thanthat at which the material starts flowing togetherwith the liquid, to beautomatically carried: off, along. said' means.

In one of the embodiments of the present invention 'of a layer ofsubstantially uniform thickness.

d the supporting surface comprises a substantially horizontally disposedtable or the like and means are provided for moving the material alongthe table in the form A slot is provided in the table near the deliveryend thereof, which extends over a distance not shorter than the width ofthe layer to be formed, while under the table and at some distancetherefrom a plate is provided which extends over the full width of theslot and reaches beyond the edge'thereof in the direction of thedelivery end of the table.- The construction of the plate is such thatthe material resting on it can form a slope, while the means'forcollecting the fraction of the material rich in moisture is disposedsubstantially under said slot.

In another embodiment of the present invention, the supporting surfacecomprises a constant speed conveyor belt onto which'thematerial to betreated is loaded at thefeed end and the means of separation comprises aplate mounted at the other end of the conveyor, the plate being disposedwith its end substantially parallel with the conveyor and at'such adistance from the upper surface thereof that the fractions high inmoisture content and low in moisture content may be separated from oneanother. Here again, the slot-like aperture should preferably beadjustable.

In yet another embodiment of thepresent invention the supporting surfacecomprises a stationary, flat plane set at an angle to the horizontal andhaving a gradient greater than that of the natural slope atapredetermined moisture content of the material low in moisture content,and the means for supplying the material is disposed at the upper feedend of the inclined plate, while at the lower end of the plate and atsome distance therefrom a separating plate is disposed which forms aslot-like aperture with the plate and extends on either side of it. Thedimensions of the plate are such that boththe fraction low in moisturecontent and the fraction high in moisture content may form a slope, thegradients of which correspond'with that of the slope of the material atthe predetermined moisture content of fractions either low in moisturecontent or'high in moisture content.

This embodiment has the advantage of comprising no moving parts foradvancing the material while the layer offers a relatively great heightfor the liquid to settle. In addition, the means of separation alsoserves as a lower support for the layer. In this embodiment the dryportion of the layer with'an admissible moisture content will flowacross the edges of the plate on the one side'and the portion rich inmoisture on the other.

It is advantageous to dispose the means of separation in such a way asto cause the moving layer slope upwards.

In this way, the settling liquid is forced to flow down along theinclined plane towards the slot resulting in a concentration of themoisture content in the material present there and thus promoting thedischarge of this moisture-rich material through the slot. Morespecifically, the means of separation is pivoted on a horizontal shaftdisposed substantially parallel with and in the elongation of theinclined supporting plane. By this measure the slope of the upper faceof the layer may be adjusted. The means of separation may consist of twoplate-shaped members on either side of the shaft, the angle between thesaid'parts being adjustable so that the discharge of the fraction richin moisture and the fraction low in moisture content may be controlledseparately.

Both in the apparatus where the layer moves on a stationary, horizontalplane and in those where the layer moves on a stationary, inclinedplane, the supporting plane may be provided, wholly or partly, withperforations through which the liquid collecting in the lowermost layerof the material may flow away, while means may be provided for carryingoff this liquid.

means are provided for supplying the material to be treated to thecentrifuge through the center thereof, the slot according to theinvention is wide enough to allow the passage of the material, whilearound this slot and at some distance therefrom a plate is providedwhich rotates together with the wall of the centrifuge and has suchdimensions that the material between the slot and the plate will form aslope whose gradient with respect to the vertical substantiallycorresponds with the gradient of the slope of the material at a givenmoisture content. In this way, the moisture content of the materialissuing through the slot can also be kept in hand, while moreovermaterial lower in moisture content can be prevented from dischargingthrough the slot. This means may comprise a vertical, or practicallyvertical, wall around the outer periphery of the slot.

In another embodiment of the present invention the slot is provided by abody of revolution, having a cylindrical or conical wall arranged torotate together with the centrifuge. The body is concentrically arrangedaround the centrifuge wall, the lower end thereof extending into thecentrifuge to within a short distance from the wall. The plate whichserves as a support for the material discharged through the slot isattached to the body. Preferably, it should be possible to displace thebody of revolution along the axis thereof.

In all the embodiments mentioned, it is of importance that materialwhich is rich in moisture that has been discharged through a slot-likeopening should be given a support under or beside the slot, so that thematerial may form a natural slope. When the moisture content in thelower layer rises above a given value, the slope will tend to becomeless steep so that automatically more material rich in moisture will becarried off. This value is attained when the material is oversaturatedwith liquid.

It thus will be seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing specific embodiment has been shown and described only for thepurpose of illustrating the principles of this invention and is subjectto extensive change without departure from such principles. Therefore,this invention includes all modifications encompassed within the spiritand scope of the following claims.

I claim:

1. A process for effecting the complete or partial removal of moisturefrom fine-grained material of substantially uniform compositioncontaining an amount of free moisture such that thepores between thegrains of said material are partially filled with liquid, whichcomprises the steps of forming a continuously moving layer of saidmoisture containing material, supporting said moving layer so that themoisture therein will settle during its movement from one part of saidlayer into an adjacent part so as to form successive layers withincreasing moisture contents, and separating a fractional layer with thehighest moisture contents from said moving layer, the grain-distributionin said fractional layer being substantially equal to the distributionin the main layer, said fractional layer being separated from saidmoving layer by removing the support thereof and then supporting thefractional layer at a position spaced from the position of supportremoval in the direction of travel of said moving layer such that thematerial of the separated fractional layer will form a slope having agradient which prevents said fractional layer from being discharged whenthe moisture decrease has not reached a predetermined value andautomatically enables discharge of the material of said separatedfractional layer when the moisture decrease has surpassed saidpredetermined value.

2. Apparatus for effecting the complete or partial removal of moisturefrom fine-grained material of substantially uniform compositioncontaining an amount of .free moisture such that the pores between thegrains of said material are partially filled with liquid comprisf ingmeans defining a surface for supporting a moving layer of moisturecontaining material along a predetermined path between a feed stationand a separation station, means for feeding material at said feedstation to said surface, said surface being disposed to support themoving layer of material so that the moisture therein will settle duringits movement from one part of said layer into an adjacent part so as toform successive layers with increasing moisture contents, the layer ofhighest moisture content being disposed adjacent said surface, and meansforming a slit-like aperture disposed in cooperating relation withrespect to said surface for separating a fractional layer with thehighest moisture contents from said moving layer and for supporting theseparated fractional layer so as to enable the material of saidseparated fractional layer to form a slope having a gradient suflicientto cause automatic flow of material with a moisture content exceeding apredetermined value.

3. Apparatus as defined in claim 2 wherein said surface-defining meanscomprises a substantially horizontal table and wherein conveyor meansare provided for efiecting continuous movement of said moving layer oversaid table.

4. Apparatus as defined in claim 2 wherein said surface-defining meanscomprises a stationary flat plate disposed at an angle to the horizontaland arranged to have the material fed at its upper end so that saidmoving layer will pass downwardly thereover, said plate having agradient greater than that of the natural slope of the material at apredetermined low moisture content.

5. Apparatus as defined in claim 4 wherein said plate is perforated.

6. Apparatus as defined in claim 4 wherein said aperture-forming meanscomprises movable elements disposed below the lower end of said plate inspaced relation thereto, said elements extending transversely of saidplate on both sides thereof and arranged to form a slope on the uppersurface of the moving layer on the plate having a gradient whichcorresponds to the natural slope of the material with a moisture contentof a maximum permissible amount.

7. Apparatus as defined in claim 6 wherein said movable elementscomprise blades independently mounted for pivotal adjustment about anaxis spaced below the lower end of and in the plane of said plate.

8. Apparatus as defined in claim 2 wherein said surface terminatesadjacent said separation station and wherein said aperture-forming meanscomprises plate means spaced from the terminal end of said surface anddisposed to engage the moving layer so that said separated fractionallayer will pass between said surface end and plate means and form aslope having a gradient sufiicient to cause flow of material with apredetermined moisture content together with the moisture, said platemeans and said main layer supporting surface enclosing a space open atone end for discharging the separated layer of highest moisture content.7

9. Apparatus as defined in claim 2 wherein said surface-defining meanscomprises a substantially horizontal table over which said moving layeris continuously moved, said table terminating adjacent said separationstation, and wherein said aperture-forming means comprises a first platehaving an end spaced from the terminal end of said table so as to form aslot through which said fractional layer passes and a second platemounted below said slot for adjustment in the direction of layermovement.

10. Apparatus as defined in claim 2 wherein said surface-defining meanscomprises an upper substantially horizontal flight of an endlessconveyor arranged to effect the continuous movement of said movinglayer, and wherein said aperture-forming means comprises a horizontallydisposed plate mounted above said upper flight for vertical adjustmentin accordance with the thickness of said fractional layer.

11. Apparatus as defined in claim 2 wherein said surface-defining meanscomprises a smooth imperforate conical wall of a centrifuge arranged toreceive the material at its axis of rotation, and wherein saidaperture-forming means'comprises plate means adjacent the upper edge ofsaid conical wall defining therewith a slot through which saidfractional layer passes.

12. Apparatus as defined in claim 11 wherein said plate means comprisesan annular plate mounted for rotation with said centrifuge conical wall,said plate having an edge portion spaced from said conical wall todefine said slot.

13. Apparatus as defined in claim 12 wherein said edge portion is spacedoutwardly from the terminal edge of said conical wall.

14. Apparatus as defined in claim 13 wherein said edge portion is spacedinwardly from the terminal edge of said conical wall closer to thecentrifuge axis of rotation, and wherein said plate includes a wallextending upwardly from said edge portion at an angle with respect tosaid conical wall.

15. Apparatus as defined in claim 2 wherein said surface defining meanscomprises a smooth, imperforate wall of a conical centrifuge arranged tohave the material fed at its axis of rotation so that the moving layerwill pass outwardly from said axis of rotation, and wherein saidaperture-forming means includes plate means arranged opposite saidslit-like aperture at the outer face of said centrifuge wall and spacedapart from said slit-like apertial-ly uniform composition containing anamount of free ture, said plate means being rotatably mounted in themoisture such that the pores between the grains of said material arepartially filled with liquid which comprises the steps of establishing acontinuous supply of said material at a feed position, imparting acentrifugal action to the supply of material at said feed position,supporting the material moving under said centrifugal action in layerformation from said feed position to a discharge position so that themoisture therein will settle during the movement between said positionsfrom the part of the layer remote from the support into the part of thelayer adjacent the support so that at said discharge position the movinglayer has a moisture content which increases in a direction toward thesupport, and continuously separating a fractional layer with the highestmoisture contents from the moving layer at said discharge position, thegrain-distribution in said fractional layer being substantially equal tothe distribution in the layer at said feed position.

References Cited in the file of this patent UNITED STATES PATENTS926,031 Stover June 22, 1909 1,818,640 Miller Aug. 11, 1931 1,880,273Pardee et al. Oct. 4, 1932 2,644,583 Cannon et al. July 7, 1953 FOREIGNPATENTS 371,753 Great Britain Apr. 28, 1932

